فهرست مطالب

Chemical Engineering - Volume:19 Issue: 2, Spring 2022

Iranian journal of chemical engineering
Volume:19 Issue: 2, Spring 2022

  • تاریخ انتشار: 1401/12/15
  • تعداد عناوین: 6
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  • Amirhossein Oudi, Abdullah Irankhah * Pages 3-20

    Optimization of the ammonia synthesis unit to increase ammonia production is studied in this line of research. In this paper, the steady-state ammonia synthesis is simulated using Aspen HysysV.11 software, by comparing the simulation results with industrial information, a mean relative error of 7.71% was obtained, which indicates the high accuracy of the simulation. Then, four effective variables were selected from 11 independent variables by the Plackett-Burman method. The effects of the Hydrogen flow in the feed stream, the Recycle stream pressure, Feed stream temperature, and Input third reactor temperature were simulated, and the response surface design method of central composite design was performed to optimize. It is obtained that the Hydrogen flow in the feed stream is equal to 6255 kmol/hr, feed stream pressure was equal to 205 bar, the temperature of excess stream inlet in the first reactor was equal to 663 K, and the temperature of stream inlet the second reactor to 677.5 K which increased to 7.5% ammonia production.

    Keywords: Ammonia synthesis, optimization, Response surface design, Central composite design, Simulation
  • Roohallah Bakhshi, Mostafa Moraveji *, Arsalan Parvareh Pages 21-35

    The polysulfone mixed matrix membranes (MMM) with different concentrations of graphene oxide (0, 0.25, 0.5 wt.% polymer) fabricated by a phase separation method. The cross-sectional structure and their upper surface were assessed by (SEM) surface roughness of the membranes assessed by (AFM). The mechanical and thermal stability of the fabricated membranes evaluated as well. Carbon dioxide, nitrogen and methane separation from natural gas considered. An increase doping graphene oxide in matrix polymer outcome in a thicker sponge layer and disappearance of the finger-like cavities. From the outer surface morphology, the MMM presentation porosity a lower surface analogy the membrane neat. The membrane tensile strength and length of the membrane at fracture point increased slightly with an increase in graphene oxide concentration. transition Glass temperature membrane increased addition graphene oxide to the structure. From TGA analysis, in presence graphene oxide, thermal stability improved. From the gas permeation test, by addition of 0.25% graphene oxide to the polymer, CO2 permeability was increased from 61.22 GPU to 76.04 GPU, while addition of 0.5 wt.% resulted in a lower permeability (69.55 GPU). Nitrogen gas permeation flux of membranes decreased from 10.93 GPU to 3.91 GPU by addition of 0.50 wt.% of graphene oxide. Methane gas permeation flux is reduced from 11.31 GPU to 6.95 GPU and 4.92 GPU by addition of 0.25% and 0.50% graphene oxide, respectively. In conclusion, an increase in graphene oxide concentration increased carbon dioxide selectivity.

    Keywords: Membrane, Gas Separation, mixed matrix membrane, graphene oxide
  • Mohammad Moaf, Omid Alizadeh *, Alireza Pendashteh Pages 36-48

    In this experimental investigation, the heat transfer and pressure drop of helical tubes with various helical diameters have been studied considering air injections. The tube was rested in vertical form and was put under constant heat flux. The flow had a downward form and the air was injected into the water stream outside the helical tube. According to the achievements, air injection has a notable impact on the heat transfer coefficient of each helical tube. The results showed that employing air bubbles could increase the Nusselt Number by up to 14%. To make an acceptable comparison among all states, the Cost Benefit Ratio (C.B.R.) factor was evaluated. The results showed that pipes with a bigger diameter had the best C.B.R factor values. It means that the air injection in the tubes with larger diameters was more beneficial than tubes with smaller helix diameters. The best value was attained for helix diameter of 18 cm and VF of 0.33 with a C.B.R factor of 0.84. Also, the worst value was 1.18 for a helix diameter of 10 cm.

    Keywords: Air Injection, Nu number, Helicoidal tube, Pressure drop, Cost-benefit ratio
  • Hamed Hoorijani, Reza Zarghami, Navid Mostoufi * Pages 49-65

    The effect of adding isopropanol (ISP) to nitrogen as the fluidizing gas on the hydrodynamics of fluidization of hydrophilic titanium nanoparticles was studied. It was shown by the pressure drop method that adding ISP reduces the minimum fluidization velocity. Wavelet transform of pressure fluctuations of the bed was employed to identify the hydrodynamic structures. Energy of hydrodynamic structures was evaluated in each fluidization mode. It was shown that ISP reduces the inter-particle attraction forces by replacing the hydroxyl group of the hydrophilic nanoparticles with an alkyl group. Energy and recurrence analysis were used to define the characteristics of fluidization when adding ISP to nitrogen gas. The energy of macro structures increased when using ISP, indicated a decrease in the number of bubbles and an increase in the bubble size due to the reduction of attraction inter-particle forces. The increase of white local areas in the recurrence plots also showed the increase of bubble size. Recurrence quantification analysis showed the increase of the larger-scale phenomena (i.e. bubbles) in the bed.

    Keywords: Fluidization, Nanoparticles, Isopropanol, wavelet transform, Recurrence analysis
  • Alireza Bahramian * Pages 66-86

    The size and lifetime of evaporating sneeze droplets in the indoor environment were studied experimentally and theoretically. The effect of indoor temperature T∞ and indoor humidity RH∞ were investigated on evaporating droplets with initial diameters of 4.9, 8.1, 17.2, and 29.7 μm. The size distribution and mean size of droplets were obtained by laser particle sizer. The experimental data showed that the possibility of aerosolized droplets increased from 25.5 to 36.1% by increasing T∞ from 18 to 30 oC and decreased from 36.1 to 13.6% by increasing RH∞ from 30 to 60%. A one-dimensional droplet evaporation model was used to estimate the droplet’s lifetime. A critical RH∞ of 40% was found; above them, the droplet lifetime exponentially increases. The effect of the initial diameter of droplets was higher than RH∞ and also the impact of RH∞ was higher than T∞ on the lifetime of aerosolized droplet nuclei. A significant effect of environmental conditions on the droplet lifetime was found over the range of 26 ○C ≤T∞ ≤30 ○C and RH∞ ≤ 40%, while its effect decreases in the range of 18 ○C ≤T∞ ≤22 ○C and RH∞ > 40%, where a minimal shrinkage of droplets take place because of the droplets hygroscopic growth. The results of this study do not imply that the COVID-19 virus will be deactivated at the end of the droplet lifetime, but it represents that controlling the indoor environment is important for virus-carrying drops.

    Keywords: Theoretical evaporation model, Indoor environment, sneeze droplets, Size distribution, droplet lifetime, Covid-19 Virus
  • Reyhane Ahmadi, Hamidreza Sanaeepur *, Abtin Ebadi Amooghin Pages 89-99

    It is crucial to design and develop new polymers with desirable characteristics. Aromatic polyimides have been attracted more attention in comparison with other polymeric materials, because of their excellent properties, such as high thermal stability, mechanical strength, and chemical resistance. In this work, two semi-aromatic polyimides (BCDA-mPDA and BCDA-Durene) were successfully synthesized from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarbocylic dianhydride (BCDA), 1,3-phenylenediamine (mPDA), and 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene) to investigate the effect of methyl functional groups on physicochemical and structural properties of the synthesized polyimides. The synthesized polyimides were characterized by proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), inherent viscosity measurement, and solubility test. FTIR and 1H-NMR results confirmed the chemical structure of the synthesized polyimides. XRD results showed that the presence of methyl bulky groups has led to increasing of amorphous regions in the polymer structure. In addition, these new polymers were soluble in various organic solvents such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP). The inherent viscosity of the synthesized polyimides was 0.65 dl/g for BCDA-Durene and 0.96 dl/g for BCDA-mPDA, respectively, which indicates the moderate molecular weight of the polymers.

    Keywords: Polymer, Polyimide, Aromatic, Methyl functional groups